The present invention relates to an overhead conveyor system.
In a known type of overhead conveyor system, rolling conveyor carriages are guided on rails, in particular for the transport of articles of clothing suspended from hangers. A conveyor line is formed by a runway rail and a drive chain which revolves horizontally endlessly above and parallel thereto, having at least one branch into another line. The conveyor carriages can be moved out of the line into a branch or secondary line by means of a pusher which is fastened to the conveyor chain and engages the back of each conveyor carriage, the pusher consisting of a carrier device and a claw which is fastened therein on a pin for swinging in a vertical plane. The claw has a first downward position (its active position) and a second position in which it is swung upward in the direction of transport (T).
In particular in the clothing industry, articles of clothing suspended from clothes hangers are hung, for purposes of filling orders or removal, on the carrier rod of single-track conveyor carriages, so-called trolleys, of an overhead conveyor system. Each of the trolleys, which travel on rails, is carried along by a driver which acts on the front track roller and is connected to a drive element which is fastened on the drive chain arranged above the runway rail.
Such an overhead conveyor system has different rail lines which are connected to each other by switches. At these switches, a trolley can be moved from the line it is on into a branching conveyor line. For this purpose, a pusher element is also fastened to the drive chain, arranged behind each trolley. When a trolley is removed from the line by a switch, the drive element comes out of engagement with the front track roller at the moment when said roller has left the rail line which it was in. The trolley then slows down and the pusher arranged behind the trolley, which continues to be driven with unchanged speed of revolution by the drive chain, engages the trolley's rear track roller which is still in the main conveyor line. In this way, the trolley continues to be pushed with its original speed into the new branch conveyor line.
In order for the trolley to be properly pushed out of the main like, the claw of the pusher must be rigid in the direction of transport. In order, however, to be able to introduce a trolley into the line between a pair of individual pushers, the claw is able to swing on the pusher in the direction of transport so that it can be lifted and passed by a trolley coming from the rear.
For this purpose, it is known to fasten the claw, which is made of plastic, to the pusher element by means of a pin which is passed horizontally and eccentrically through one end of the claw.
With the known equipment, there are two basic types of collision which can seriously interfere with the operation of the conveyor when a trolley is being removed from a main line into a branch line.
In the first case, after the switch has been passed over by the front track roller of the conveyor carriage, the switch may spring back, so that while the front roller has been removed from the line and placed in the new conveyor line, the rear roller has not been released from the line and so remains in the old conveyor line. Since the U-shaped carrier rods of the conveyor carriages are mounted turnably in the carrier brackets which receive the track rollers, the pusher continues to push the trolley which is now in transverse position until the parallel distance between the front roller and the rear roller has reached the length of the carrier rod. Further transport movement is not possible. If the conveyor chain is not then turned off, there will be a fracture of material.
In the second case, the conveyor carriage is properly removed from the main line but the new section of line, for whatever reason, is occupied and the trolley strikes against an obstacle. If the obstacle is so close to the main conveyor line that the trolley cannot enter completely into the new conveyor line, it cannot be transported further by the pusher. In this case also there will inevitably be a fracture of material if the drive is not shut off immediately.